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Special Notice #342: PU CMa, then IY UMa and MR UMa next HST/COS targets

March 18, 2013:  Further to AAVSO Alert Notice 471 (http://www.aavso.org/aavso-alert-notice-471), HST/COS is scheduled to observe the SU UMa-type dwarf nova PU CMa:

PU CMa   2013 March 22 00:00:43 through 02:36:08 UT

The HST observations of PU UMa may be cancelled/postponed, as PU CMa is currently in outburst, according to observations reported to the AAVSO:

2013 March 17.02097 UT, 15.24 V +/-0.08, Shawn Dvorak, Clermont, FL;
17.43542, <11.8, Hiroshi Matsuyama, Kannibmla, QLD, Australia;
17.46080, 15.157 CV +/-0.017Gordon Myers, Hillsborough, CA;
17.53750, <15.2, Andrew Pearce, Nedlands, WA, Australia;
18.403, 11.2, Rod Stubbings, Tetoora Road, VIC, Australia;
18.4042, 11.87, Peter Nelson, Ellinbank, VIC, Australia;
18.46860, 11.755 CV +/-0.004, Myers;

This may be a superoutburst, so the system may still be too bright for the HST instrumentation by March 22. However, please follow PU CMa closely at least through March 23, in case it fades to below the safe threshold in time. Your observations will be critical in determining whether it will be safe for HST to observe PU CMa.

The next HST/COS targets are scheduled to be IY UMa:

IY UMa     2013 March 29 23:43:52 through March 30 02:18:13 UT
(SU UMa-type dwarf nova, V=18.4 at minimum, V=13 at maximum)

and MR UMa:

MR UMa  2013 April 1 UT    time to be announced
(SU UMa-type dwarf nova, V=16.7 at minimum, V=12.3 at maximum)

Observations are crucial beginning now and continuing through one night after the HST observations. About 24-36 hours before the planned observations the HST/COS scheduling team will make the final decision whether to observe each system. Both of these systems are potentially bright enough at maximum to cause real difficulties for HST, so it will be essential to know the outburst status and brightness.

As instructed in AAVSO Alert Notice 471, for CCD observers, simultaneous photometry [shortly before, during, and after the HST observations] would be ideal. For the magnitude estimates, a nightly V measurement from now through the HST observations and a day beyond would be best. If positive visual observations are possible, they are welcome, as are visual fainter-than observations fainter than magnitude 15.0.

Coordinates (2000.0)
PU CMa          R.A. 06 40 47.69   Dec. -24 23 13.9
IY UMa          R.A. 10 43 56.74   Dec. +58 07 32.1
MR UMa          R.A. 11 31 22.39   Dec. +43 22 38.5

Charts may be created using the AAVSO Variable Star Plotter (http://www.aavso.org/vsp).

Please report observations as soon as possible to the AAVSO International Database using the names PU CMa, IY UMa, and MR UMa, respectively. If an outburst is detected, please report observations immediately.  Many thanks!

This AAVSO Special Notice was compiled by Elizabeth O. Waagen.

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